The present invention relates to a ship position control system for use in a small ship such as a pleasure boat or a fishing boat.
In the first related art (Patent Application Publication (KOKAI) Hei 8-192794), the ship's course is automatically controlled by operating a helm or thruster at a predetermined control ratio according to a ship speed based on respective detection signals from an direction sensor, a position sensor, and a speed sensor.
In the second related art disclosed in Patent Application Publication (KOKAI) Hei 8-58696, a ship keeps a predetermined position, operating two propulsion units in a twin-screw vessel respectively according to a difference between hull positions based on respective detection signals which are output from a direction sensor, a position sensor, a vane-anemometer, and a tidal sensor.
These pleasure boats or fishing boats need to stay at a constant point to provided gratifying fishing.
However, in the first the related art, the hull is not maintained or stayed at a predetermined point of the fishery since a course is controlled only by speed. Meanwhile, in the second related art, a predetermined speed is needed to actuate a rudder effectively since the boat must be returned to a target area by controlling propulsion forces generated by two propulsion units in the two-axle ship. Therefore, a ship position control system in the second related art is not effective for precise ship position control to maintain or stay the boat at a constant point in the fishery. In addition, it does not help but conclude that a time required for ship position correction is prolonged to thus degrade a control response characteristic since the ship position must be corrected by controlling respective propulsion forces generated by the two propulsion units.